Arthropod Agents and Vectors of Diseases Parasitic Helminths and Arthropod Agents and Vectors of Diseases Dr. Ibrahim Alkhalife

Arthropod Agents and Vectors of Diseases Parasitic Helminths and Arthropod Agents and Vectors of Diseases Objectives: By the end of this lecture the student should be able to : Name the three main groups of parasitic helminths and their characteristic morphological features . Describe the life cycle of Ascaris lumbricoides as an example of parasitic helminths . Discuss the role of arthropods as agents and as vectors of diseases in humans. Give examples of the main arthropod vectors of diseases.

Classification of Parasites Helminths Protozoa Multicellular Specialized cells Unicellular Single cell for all function A- Round worms = Nematodes cylindrical, un-segmented (Ascaris) B- Flat worms 1-Trematodes: leaf-like, un-segmented. 2-Cestodes: tape-like, segmented Amoebae: move by pseudopodia. Flagellates: move by flagella. Ciliates : move by cilia Apicomplexa (sporozoa) Tissue parasites

Location of helminths in the body: Intestinal helminths: Tissue helminths:

Nematodes (round worm) intestinal Nematode General features Elongated worm, cylindrical, unsegmented and tapering at both ends. Variable in size, measure <1 cm to about 100cm. Sex separate and male is smaller than female

Ascaris lumbricoides (roundworm)

Ascaris lumbricoides (roundworm) The commonest intestinal helminthes can cause infection to human. Found in jejunum and upper part of ileum. Female ( 20-40 cm) which is longer than male ( 10-15 cm) . Feed on semi digested food.

Ascaris lumbricoides life cycle

a Ascaris lumbricoides

Life cycle of Ascais Lumbricoides It infect human when man ingest fertilized egg contaminated with food or water This fertilized egg become a Larva that penetrate the wall of the duodenum It will enter the blood stream to the heart, liver and enter the pulmonary circulation and stay in the alveoli

Life cycle of Ascais Lumbricoides (cont.) It will grow and molts for three weeks then Larva passes from respiratory system to be coughed up, swallowed, returned to the small intestine where it mature to adults male & female fertilization take place producing eggs which pass in stool.

Pathogenicity Migrating LARVA : Adult WORM: Ascaris pneumonia, some times LARVA reach aberrant sites like brain, heart or spinal cord can cause unusual disturbance. Adult WORM: The worm consumes proteins and vitamins from host’s diet and leads to malnutrition. Can cause intussusception, intestinal ulcers and in massive infection can cause intestinal obstruction.

Classification of Parasites Helminths Protozoa Multicellular Specialized cells Unicellular Single cell for all function A- Round worms = Nematodes: cylindrical, un-segmented (Ascaris) B- Flat worms 1-Trematodes: leaf-like, un-segmented. 2-Cestodes: tape-like, segmented Amoebae: move by pseudopodia. Flagellates: move by flagella. Ciliates: move by cilia Apicomplexa (sporozoa): Tissue parasites

The Trematodes flat worm, unsegmented, leaf like Fasciola hepatica

Fasciola Hepatica

Cestode

Taenia saginata Example of a Cestode,Tapelike worm segmented.

MEDICAL IMPORTANCE OF ARTHROPODS 1) As aetiologic agents (causes) of diseases: Tissue damage Induction of hypersensitivity reactions. Injection of poisons Entomophobia (acarophobia) 2) As vectors of diseases: I: Mechanical transmission - simple carriage of pathogens. II: Biological transmission: cyclical propagative Cyclopropagative III: Transovarian transmission

Scabies as tissue damage example of Arthropod

الجرب Scabies

Important arthropod vectors for human diseases House fly (Musca domestica) الذباب المنزلي Mechanical transmission of many viruses, bacteria and parasites. Mosquitoes البعوض Anopheles: malaria, filariasis Culex: filariasis, viruses Aedes: yellow fever, dengue fever, Rift Valley Fever Lice القمل Body louse: vector for Relapsing fever, typhus and trench fever. Fleas البراغيث Rat flea: is vector for plague due to Yersinia pestis. Ticks القراد Soft ticks: some are vectors for: Borrela duttoni Hard ticks Include vectors for Babesiosis (protozoa), Q fever and Rocky mountain spotted fever Tse tse fly (Glossina) ذبابة التسي Vector for African Trypanosomiasis (African sleeping sickness) Black fly (Simulium)الذبابة السوداء Vector for Onchocerca (river blindness) Sand fly (Phlebotomus) ذبابة الرمل Vectors for Leishmania and sandfly fever virus. Cyclops Vector for Dracunculus medinensis

LICE Pediculus humanus

Mosquitoes : Cosmopolitan, more than 3000 species. Larval and pupal stages always aquatic Mouth parts in female adapted to piercing and sucking blood. Genus and species distinguished by morphology of adult and deveopmetal stages.

Phlebotomus sand fly

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